Factorial structure of the Youth Self-Report. Principal components/varimax analyses of the YSR problem items (Achenbach, 1991) were performed for each gender group, in a sample of 2833 students aged 11-18. From the analysis of the common items found in the nine first-order factors derived for each gender, the following core syndromes were derived, that were slightly different from those obtained by Achenbach: Depression, Verbal aggression, Delinquent behaviour, Thought problems, Somatic complaints, Social (withdrawn) problems, Attention-seeking behaviour, and Phobic-anxious behaviour. Second-order factor analysis of the eight syndrome scales reflected a distinction between internalizing vs. externalizing psychopathology (i.e., emotional / conduct disorders), to a great extent similar to that found in some other multivariate analyses.